This invention relates to cardiac assist devices which are placed within the body, or in the blood stream, and driven by a source of fluid such as air, helium or carbon dioxide. It is of particular relevance to temporary devices for insertion in the vascular system, such as intra-aortic balloon pumps and the like, which have a balloon or bladder formed of a thin membrane.
It is necessary in devices of this type to guard against leakage of the drive fluid through tears or cracks in the balloon membrane. Current methods of leak detection rely on detecting changes in gas pressure in the closed fluid drive system while the pump is in operation. One problem with this method is the relatively low sensitivity of the technique, which can detect gas leaks of about 3 cc/minute. Considering that hundreds of small gas bubbles may be formed in the bloodstream for each cubic centimeter of gas leakage through a small hole, this detectable leakage threshhold may be seen to pose a significant risk for the patient. It is therefore desirable to detect leakage of the fluid system faster or with greater sensitivity.